The Transporter-Opsin-G protein-coupled receptor (TOG) Superfamily consists of integral membrane proteins, usually of 7 or 8 transmembrane alpha-helical segments (TMSs), that share a common evolutionary origin. The designation, the Transporter/Opsin/G protein-coupled receptor (TOG) superfamily, is based on the currently best-characterized families present in this superfamily. In addition to; (1) ion-translocating microbial rhodopsins (MR; TC# 3.E.1] and (2) G protein-coupled receptors (GPCRs; TC# 9.A.14], including visual rhodopsins (VRs), members of the following families share a common origin with microbial, invertebrate and vertebrate rhodopsins: (3) Sweet sugar transporters (Sweet; TC# 2.A.123], (4) nicotinamide ribonucleoside uptake permeases (PnuC; TC# 4.B.1], (5) 4-toluene sulfonate uptake permeases (TSUP; TC# 2.A.102], (6) Ni²⁺–Co²⁺ transporters (NiCoT; TC# 2.A.52], (7) organic solute transporters (OST; TC# 2.A.82], (8) phosphate:Na⁺ symporters (PNaS; TC# 2.A.58] and (9) lysosomal cystine transporters (LCT; TC# 2.A.43].